This invention relates to reclosable, sealable fasteners, such as for bag closures.
Extruded interlocking profile fasteners, such as those known to be marketed under the trade name “ZIPLOC”, have been employed as closures for bags and other packaging for many years. Such closures have the advantage of providing a reasonably reliable seal across the bag opening, as well as holding the two sides of the bag opening together. Furthermore, they are readily produced by known extrusion methods, their principle of engagement being the interlocking of mating longitudinal features having extrudable, complementary shapes. Thus, such fastening is sometimes referred to as ‘rib and groove’ fastening. Forming the head of the rib to be wider than the neck of the groove creates a ‘snap’ engagement (during which one or both of the profiles resiliently deforms) to retain the rib within the groove until pulled out. A relatively tight fit of the rib within its groove can provide an effective seal. Rib and groove closure strips and the film forming the sides of their associated bags are commonly made separately and then joined.
More recently, advancements in the production and design of hook and loop fasteners have resulted in cost-effective alternatives to rib and groove fastening for releasably securing bag openings in a closed condition. The principle of engagement of hook and loop fasteners involves the statistical engagement of a field of hooks, or male-type fastener elements, with a field of loops or fibers. Thus, hook and loop fasteners do not require precise alignment for closure. Also, face-to-face hook and loop closures form many small passages between the engaged fields of hooks and loops, enabling air (and, in some cases, liquids) to migrate across the closure. For some applications, such free ventilation is desirable. In some other applications, however, a liquid or air-tight seal, or an advantageously lower leak rate, would be preferred.